Image intensifier having optically isolated cells and method of constructing same



June 20, 1967 J. E. DUEKER ETAL 3,327,122

IMAGE INTENSIFIER HAVING OPTICALLY ISOLATED CELLS AND METHOD OF CONSTRUCTING SAME Filed Dec. 12, 1963 INVENTORS JAMES E. DUEKER ALBERT E. LOMBARD JR.

Br FIG. 6. 4545; ,1

firmwvzs United States Patent 3,327,122 WAGE INTENSIFIER HAVING OPTICALLY ISOLATED CELLS AND METHOD OF CON- STRUCTING SAME James E. Dueker and Albert E. Lombard, Jr., St. Louis County, M0,, assignors to McDonnell Aircraft Corporation, St. Louis County, Mo., a corporation of Maryland Filed Dec. 12, 1963, Ser. No. 330,106 17 Claims. (Cl. 250213) The present invention relates generally to optical and electro-optical devices and more particularly to an image intensifier device constructed of a plurality of individual optically isolated image intensifier cells and to the method of making same. i

Image intensifiers, sometimes called light amplifiers, have been constructed heretofore and some of the known devices have been made of semi-conductor materials and the like and have also been constructed of a plurality of individual cells optically isolated from one another. The known constructions, however, are difficult, time consuming and expensive to make and are structurally different from the present device. Furthermore, in all known constructions a relatively large portion of the total surface area is taken up by optical shielding material leaving a relatively small portion of the surface area available for light amplification.

These and other disadvantages and shortcomings of the known image intensifier devices and methods of making same are overcome by the present invention which features an image intensifier construction formed by a plurality of individual intensifier cells optically isolated from each other. The present device also includes improved means for making electrical connections thereto. The present device is also of relatively rugged construction and has more usable surface area in relation to its total surface area than any known construction. Furthermore, the present invention covers a novel method of making an image intensifier element.

It is therefore a principal object of the present invention to provide an improved image intensifier and an improved method of making same.

'Another object is to provide improved means for optically isolating a plurality of adjacent image intensifier cells from each other in an image intensifier element.

Another object is to improve the light magnification characteristics of image intensifier elements.

Another object is to increase the ratio of usable to nonusable surface area in light amplifiers and the like.

Another object is to provide an improved method of making multi-cell image intensifier devices which method lends itself to making the individual cells in dilferent sizes and shapes.

Another object is to improve the optical resolution characteristics of image intensifiers and the like.

Another object is to provide a relatively rugged multicell image intensifier.

Another object is to reduce the cost and simplify the construction of image intensifier elements and the like.

Another object is to provide improved means for attaching electrical connections to controllable image intensifier devices and the like.

These and other objects and advantages of the present invention will become apparent after considering the following detailed specification of a preferred embodiment thereof in conjunction with the accompanying drawing, wherein:

FIG. 1 is an enlarged perspective view of a layered element from which an image intensifier device constructed according to the present invention is to be made;

FIG. 2 is an enlarged perspective view of a partially constructed image intensifier device;

FIG. 3 is an enlarged perspective view of an image intensifier device constructed according to the present invention;

FIG. 4 is a further enlarged fragmentary cross-sectional view taken on line 44 of FIG. 3;

FIG. 5 is a cross-sectional view taken on line 55 of FIG. 4; and

FIG. 6 is a fragmentary cross-sectional view similar to FIG. 4 but showing a modified form of .the subject device.

Referring to the drawing by reference numbers, number 10 refers to a layered element to be used in making an image intensifier device constructed according to the present invention. The element 10 includes a layer 12 formed of photoconducting material, a layer 14 formed of optical absorbing material having a predetermined controlled opacity, and a layer 16 formed of electroluminescent material such as electroluminescent phosphor and the like. These materials are commonly used in the construction of image intensifiers. The optical absorbing layer 14 serves as the mechanical support for the structure, and the layers 12 and 16 are attached to the layer 14 by a suitable process such as by evaporation in a vacuum or by a sputtering process.

The layered element 10 is dissected by first cutting it into parallel slices running one way. These slices are then recemented together in the same way to reconstruct the original element using an optically opaque, non-electrical conducting adhesive 18. The adhesive 18 is used to optically isolate each of the strips from the other strips. When the slices have been recemented as aforesaid, the element is again sliced into strips but this time .the strips are made perpendicular to the aforesaid strips. These second strips are then again recemented in the same way using the same adhesive 18. The reconstructed element 22 is in the form of a plurality of individual image intensifier cells 20 with adhesive 18 optically isolating each of the individual cells from the other cells. This form of element is highly desirable because it provides improved resolution properties and it also provides a structure in which most of the surface area is formed by the cell elements 20 themselves and in which only a relatively small portion of the total surface area is taken up by the opaque adhesive 18.

After the above described checkerboard element 22 has been constructed, transparent electrical conducting layers 24 and 26 are attached respectively to the top and bottom surfaces thereof. The layers 24 and 26 can be applied in sheet form, they can be applied by an evaporation and deposition in a vacuum, or they can be applied in any other suitable way. The layers 24 and 26 provide electrical contact to both opposite surfaces of every cell 20, they strengthen the construction, and being transparent, they do not interfere with the normal operation thereof.

The layers '24 and 26 are also connected by leads 28 and 30, respectively, to a voltage source 32. The voltage source 32 is preferably a controlled source which regulates the intensity of an output light image appearing on the completed image intensifier device 34 by varying the voltage applied thereacross in a manner well known to the art.

FIG. 4 is an enlarged fragmentary view of a few of the individual optically isolated intensifier cells in the completed element 34. In all of the drawings, the individual parts are shown much larger and thicker than they actually are for illustrative purposes.

The recementing of the slices to form the final checkerboard construction of the subject device can be accomplished in several dilferent ways including applying the adhesive 18 by brushing, dipping, spraying, vapor deposition, or any other suitable way depending upon the type of adhesive employed. It may also be necessary to cure the adhesive by placing the recemented element 22 in a controlled temperature environment. Once the element 22 is completed the electrical conducting layers 24 and 26 are attached being sure that they engage the upper and lower surfaces of each of the cell elements. This is a relatively simple matter if all of the cells have their upper and lower surfaces respectively in the same planes. Furthermore, by having the electrical conducting layers 24 and 26 extend over the entire opposite surfaces of the element 22 applied voltages act uniformly over the entire finished element 34 which is highly desirable.

It is also contemplated to make the individual cells in sizes and shapes dififerent from those shown as required. For example, the elements can be made in almost any geometric form which enables the element to be recemented so that each adjacent cell is optically isolated from its neighbors.

The layer 14 of controlled opacity provides optical feed-back in the subject device which is desirable because it improves the light gain characteristics and at the same time prevents energization of adjacent elements since each element is optically isolated from its. neighbors.

Any image forming optical system can be used to form an image on the conductor layer 24 and on the photoconducting materialll. Each cell of the subject device then becomes photoconducting depending on the brightness of the image incident thereon. Those elements that become conducting cause the electric field intensity in the respective cells to increase. This increased field intensity in turn causes the electroluminescent phosphor in layer material 16 associated therewith to emit visible light. A duplication of the input image on the transparent conductor layer 24 is now observed as visible light on the other transparent conductor layer 26. At the same time, optical feed-back from the electroluminescent material 16 takes place in each of the respective cells. This feed-back is to the associated photoconducting material in the same respective cells. The amount of the feed-back is controlled by the degree of opacity of the optical absorbing material in the layer 14. No feed-back can occur from one cell to another, however, because of the opaque cement 18 which is positioned between adjacent cells. Thus it can be seen that the present device uses optical feed-back advantageously to improve the light amplification characteristics thereof. The present device also provides improved means to eliminate interference between adjacent cells in the structure, it eliminates the need for connecting circuits or Wires to each of the individual cells, it provides a structure which is relatively easy to make, it is highly reliable and it is of rugged construction. Furthermore, the several layers forming the device are particularly well suited to being constructed by vapor deposition and other well known techniques.

The subject device can be used to convert invisible infra-red and ultra-violet radiation images to visible images, and it can be used to amplify a visible or invisible image. Furthermore, the intensity of the outputimage can be varied simply by varying the voltage applied to the conductor layers 24 and 26.-In like manner, the subject device can also convert X-ray images to visible light images with the same type of amplification available. In

other words, the present device can be used to amplify or intensify an image in any situation regardless of the form or frequency of the input image. The subject device can also be employed with many existing devicesand machines where light amplification and good resolution are required.

An alternate method of constructing a checkerboard intensifier cell configuration according to the present invention is illustrated in FIG. 6 and primes are used to identify the parts of the modified cell that correspond to parts of the cell shown in FIGS. 3-5 The alternate method includes depositing layers 12 of photoconducting mate- .4 rial and 16' of electroluminescent material on the layer 14 of controlled opacity by a vapor deposition process or the like, and then cutting throughthe layers 12' and '16 to form a checkerboard array using a beam such as an electron beam. To do this the electron beam is controlled to penetrate the layers-'12 and 16' by directing it thereagainst from the respective opposite sides of the structure. The beam, however, should not completely penetrate or cut through the layer 14. Cutting with the beam therefore should be made from two directions and should be carefully controlled. After completion of the cutting by the electron beam, the cut portions or valleys are then filled with an optically opaque material similar to the adhesive 18 used in the process previously described. The adhesive material can be applied by wiping an opaque viscous material on the surfaces to fill the cut away portions or valleys, or it can be applied by brushing, spraying or polishing operations.

Still another alternate way of construction the subject device again using the electron beam is to deposit the layers 12, 14', 16 and 26 on an external substrate such as on a piece of glass or other suitable material, and use the beam to slice through the layers 12, 14' and 16' but not through the layer 26'. The non-light conducting mate rial would then be wiped or otherwise inserted into the voids or ents after which the transparent light conducting layer 24' would be applied to complete the assembly.

Thus there has been shown and described a novel image intensifier and a novel method of construction same which fulfills all of the objects and advantages sought therefor. Many changes, variations, modifications and other uses and applications for the subject devices and other forms of making the same will become apparent to those skilled in the art after considering this specification and the accompanying drawing which are presentedfor illustrative purposes only. All such changes, variations, modifications and other uses and applications and methods of constructing same which do not depart from the spirit and scope of this invention are deemed to be covered by the invention which is limited only by the claims which follow.

What is claimed is:.

1. An image intensifier device comprising a plurality of individual image intensifier cells each of which includes a first layer of material having photocondueting properties, a second layer of material having electroluminescent properties, and a layer of optical absorbing material of predetermined opacity positioned therebetween, adhesive means around the edges of each of said cells connecting adjacent cells together to form a unified wafer-like structure thereof with corresponding layers in each cellarranged in a plane, said adhesive material including. nonlight conducting material which optically isolates each cell from the other cells, a first layer of transparent electrical conducting material in surface-to-surface contact with the 'photoconducting layer of each cell on the opposite side thereof from the layer of optical absorbingmaterial, and a second layer of transparent electrical conducting material in surface-to-surface contact with the electroluminescent layer of each cell on the opposite side thereof from the layer of optical, absorbing material. e

2. An image intensifier device comprising a wafer ele-v ment constructed of a plurality of individual image intensifier cells each having opposite surfaces and a peripheral surface therearound, adhesive means on the peripheral surface of each cell for attaching adjacent cell together to form an image intensifier wafer thereof, said adhesive means being non-light conducting to optically isolate each of said cells from the other cells in the wafer, each of said cells comprising a first layer of material having photot conducting properties and forming one of said opposite surfaces, a second layer of material having electroluminescent properties forming the other of said opposite surfaces, and a layer of optical absorbing material of predetermined opacity positioned therebetween, said optical absorbing layer providing support for the waferelement, a first transparent electrical conducting layer attached to one of said opposite wafer surfaces and in surface-to-surf-ace electrical contact with the photoconductive layers of said cells, and a second transparent electrical conducting layer attached to the opposite wafer surface and in surface-to-surface electrical contact with the electroluminescent layers of said cells.

3. The image intensifier device defined in claim 2 wherein each of said cells are substantially square and arranged in perpendicular rows and columns in the wafer.

4. The image intensifier device of claim 2 wherein a controlled voltage source is connected between said first and said second transparent electrical conducting layers.

5. The imageintensifier device of claim 2 wherein said optical absorbing layer of controlled opacity permits optical feed-back from the electroluminescent layer to the photoconducting layer in each cell to control the light gain thereof.

6. The image intensifier defined in claim 2 wherein said photoconducting layers and said electroluminescent layers of said cells are formed of semi-conductor materials.

7. A light amplifier device comprising a wafer constructed of a plurality of individual image intensifier cells each including a first layer of material having photoconducting properties, a second layer of material having electroluminescent properties, and a layer of optical absorbing material of predetermined opacity characteristics positioned therebetween, means cementing said cells together into a wafer structure of unified construction with the aforesaid layers respectively arranged coplanar in the wafer, said cementing means extending around the peripheries of said layers in each cell and including an adhesive material having non-light conducting properties to optically isolate each cell from the other cells, a first transparent electrical conducting layer attached to one side of the wafer structure in electrical communication with the photoconducting layer of each of said cells, a second transparent electrical conducting layer attached to said wafer on the opposite side thereof from the first electrical conducting layer and in contact with the electroluminescent layer, means connecting said first and said second electrical conducting layers across a source of controlled voltage so that when an image impinges on the first electrical conducting layer and on said photoconducting layer it Will be reproduced by said wafer as a visible image on the electroluminescent layer and on the said second electrical conducting layer, said reproduced image being optically intensified in the said cells by the source of controlled voltage, and said optical absorbing layer being constructed of a material which permits a controlled portion of the visible image produced in the electroluminescent layers to be fed back to the photoconducting layers to increase the intensity of the visible image in each of said cells, said nonlight conducting cement preventing the input illumination and the feedback illumination from passing between the cells of the wafer.

8. A method of making an image intensifier device comprising the steps of forming an element of wafer-like construction having a first layer of photoconducting material, a second layer of electroluminescent material and a third layer of optical absorbing material of predetermined opacity positioned therebetween, slicing the said element in one direction nito a plurality of strips, cementing said strips together with the same layer arrangement using an adhesive between the strips having non-light conducting properties, reslicing the said cemented together strips at an angle relative to the aforesaid slices to form a plurality of strips running in another direction, cementing the said last named strips together while maintaining the same layer arrangement using an adhesive between adjacent strips having non-light conducting properties, attaching a first layer of transparent electrical conducting material to one surface of the cemented together structure, and attaching a second layer of transparent electrical conducting material to the opposite surface of said cemented together structure.

9. The method defined in claim 8 wherein said waferlike construction is formed by steps employing evaporating and depositing said first and second layers on opposite sides of said third layer.

10. A method of making an image intensifier device comprising the steps of forming an element of wafer-like construction having a first layer of photoconducting material, a second layer of electroluminescent material, and a third layer of optical absorbing material of controlled opacity positioned between said first and said second layers and mechanically supporting said first and said second layers, cutting said wafer-like construction in one direction into a plurality of strips, cementing said strips together to reform the wafer-like construction maintaining the layer arrangement therein using an adhesive betwen adjacent strips having non-light conducting properties, reslicing said cemented together structure at an angle relative to the aforesaid slices to form a plurality of different strips each of which includes portions of the aforesaid strips, cementing said different strips together to reform the wafer-like construction while maintaining the same layer arrangement using an adhesive between adjacent strips having non-light conducting properties, attaching a first layer of transparent electrical conducting material to one surface of the reconstructed structure, and attaching a second layer of transparent electrical conducting material to the opposite surface of said reconstructed structure.

11. The method of making an image intensifier device defined in claim 10 wherein said photoconducting material is deposited in a layer on the optical absorbing material using an evaporation and deposition step.

12. The method of making an image intensifier device defined in claim 10 wherein said electroluminescent material is deposited in a layer on the optical absorbing material using a controlled evaporation and deposition process.

13. The method of making an image intensifier device defined in claim 10 wherein said second slicing step is performed on the construction at right angles to the first slicing step.

14. A method of making an image intensifier device comprising the steps of forming an element of wafer-like construction having a first layer of photoconducting material, a second layer of electroluminescent material, and a third layer of optical absorbing material of predetermined opaqueness positioned between said first and said second layers and mechanically supporting said first and said second layers, cutting said wafer-like construction in one direction into a plurality of strips, cementing said strips together to reform the wafer-like construction using an adhesive between adjacent strips, said adhesive having nonlight conducting properties, reslicing said cemented together structure at an angle relative to the aforesaid slices to form a plurality of different strips each of which includes portions of the aforesaid strips, and cementing said different strips together to reform the wafer-like construction while maintaining the same layer arrangement therein and using an adhesive having non-light conducting properties to connect said adjacent strips.

15. The method of making an image intensifier defined in claim 14 including the steps of providing electrical connections to each of said optically isolated layer portions of photoconducting and electroluminescent material.

16. An image intensifier device comprising a first layer of optical absorbing material of predetermined opacity, a second layer of material having photoconducting properties attached to one side of the aforesaid layer, a third layer of material having electroluminescent properties attached to the opposite side of said first layer, said electroluminescent and photoconducting layers being constructed of a plurality of individual elements spaced from each other, a non-light conducting substance positioned in the spaces between the individual electroluminescent and photoconducting elements on each side of the device to optically isolate each of said elements from the others in the layers, a first layer of transparent electrical conducting material attached to the photoconducting layer on one side of said device, and a second layer of transparent electrical conducting material attached to the electroluminescent layer on the opposite side of said device.

17. A method of making an image intensifier wafer comprising the steps of forming a wafer-like element having a first layer of optical absorbing material of predetermined opacity, depositing a second layer having photoconducting properties on one side of the first layer, depositing a third layer having electroluminescent properties on the opposite side of said firs-t layer, exposing predetermined areas of said second and third layers to an energy beam capable of penetrating said second and third layers respectively to form a plurality of distinct portions with void spaces between adjacent portions in each of said layers, filling said void spaces with a material having non- 8 light conducting properties to optically isolate the distinct portions of said second and third layers from each other, and attaching a respective layer of transparent electrical conducting material in contact with the optically isolated distinct portions of said second and third layers on oppo-- site sides of the wafer-like element.

References Cited UNITED STATES PATENTS 2,732,469 1/ 1956- Palmer.

2,792,447 5/ 1957 Kazan 250213 X 2,942,120 6/ 1960 Kazan 250-213 2,999,941 -9/1961: Klasens 25 02t13 3,002,102 9/1961 Palmer 250213 RALPH G. NILSON, Primary Examiner.

I. D. WALL, Assistant Examiner. 

1. AN IMAGE INTENSIFIER DEVICE COMPRISING A PLURALITY OF INDIVIDUAL IMAGE INTENSIFIER CELLS EACH OF WHICH INCLUDES A FIRST LAYER OF MATERIAL HAVING PHOTOCONDUCTING PROPERTIES, A SECOND LAYER OF MATERIAL HAVING ELECTROLUMINSECENT PROPERTIES, AND A LAYER OF OPTICAL ABSORBING MATERIAL OF PREDETERMINED OPACITY POSITIONED THEREBETWEEN, ADHESIVE MEANS AROUND THE EDGES OF EACH OF SAID CELLS CONNECTING ADJACENT CELLS TOGETHER TO FORM A UNIFIED WAFER-LIKE STRUCTURE THEREOF WITH CORRESPONDING LAYERS IN EACH CELL ARRANGED IN A PLANE, SAID ADHESIVE MATERIAL INCLUDING NONLIGHT CONDUCTING MATERIAL WHICH OPTICALLY ISOLATES EACH CELL FROM THE OTHER CELLS, A FIRST LAYER OF TRANSPARENT ELECTRICAL CONDUCTING MATERIAL IN SURFACE-TO-SURFACE CONTACT WITH THE PHOTOCONDUCTING LAYER OF EACH CELL ON THE OPPOSITE SIDE THEREOF FROM THE LAYER OF OPTICAL ABSORBING MATERIAL, AND A SECOND LAYER OF TRANSPARENT ELECTRICAL CONDUCTING MATERIAL IN SURFACE-TO-SURFACE CONTACT WITH THE ELECTROLUMINESCENT LAYER OF EACH CELL ON THE OPPOSITE SIDE THEREOF FROM THE LAYER OF OPTICAL ABSORBING MATERIAL. 